Reliability and relevance of radiographic measures of metatarsus primus elevatus and arch alignment in individuals with midfoot arthritis and controls

Background: Low arch alignment and metatarsus primus elevatus (MPE) have been postulated to increase dorsal compressive stresses in the joints of the medial column of the foot and to contribute to the development of degenerative changes. The primary purposes of this study were 1) to examine the relationship between radiographic measures of arch alignment and MPE and 2) to assess arch alignment and MPE in individuals with midfoot arthritis and in asymptomatic controls. The secondary aim was to examine the reliability of radiographic measures of arch alignment and MPE. Methods: Radiographic measures of arch height and MPE were quantified on 28 individuals with midfoot arthritis and 22 individuals in a control group. Reliability was assessed using the intraclass correlation coefficient (ICC). The Pearson product moment correlation (r) was used to assess the relationship between arch alignment and MPE. Between-group differences were assessed using a two-sample t test (α = 0.05). Results: Good to excellent reliability was noted for measures of arch height (ICC[2,3] = 0.919-0.994) as well as MPE (ICC[2,3] = 0.891-0.882). A modest positive association was noted between normalized cortical elevation and normalized navicular height (r = 0.274, P =.030) and calcaneal inclination angle (r = 0.263, P =.035). Individuals with midfoot arthritis demonstrated lower arch alignment, reflected in a significantly higher calcaneal-first metatarsal angle (P =.002), lower calcaneal inclination angle (P =.004), and lower normalized navicular height (P,.001) compared with controls. No evidence was found to support between-group differences in lateral intermetatarsal angle (P =.495) and normalized cortical elevation (P =.146). Conclusions: These findings provide objective data establishing the reliability of measures of MPE and arch alignment and their potential clinical significance.